source: trunk/doc/src/q3memarray.qdoc@ 498

/****************************************************************************
**
** Copyright (C) 2009 Nokia Corporation and/or its subsidiary(-ies).
** Contact: Qt Software Information (qt-info@nokia.com)
**
** This file is part of the documentation of the Qt Toolkit.
**
** $QT_BEGIN_LICENSE:LGPL$
** Commercial Usage
** Licensees holding valid Qt Commercial licenses may use this file in
** accordance with the Qt Commercial License Agreement provided with the
** Software or, alternatively, in accordance with the terms contained in
** a written agreement between you and Nokia.
**
** GNU Lesser General Public License Usage
** Alternatively, this file may be used under the terms of the GNU Lesser
** General Public License version 2.1 as published by the Free Software
** Foundation and appearing in the file LICENSE.LGPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU Lesser General Public License version 2.1 requirements
** will be met: http://www.gnu.org/licenses/old-licenses/lgpl-2.1.html.
**
** In addition, as a special exception, Nokia gives you certain
** additional rights. These rights are described in the Nokia Qt LGPL
** Exception version 1.0, included in the file LGPL_EXCEPTION.txt in this
** package.
**
** GNU General Public License Usage
** Alternatively, this file may be used under the terms of the GNU
** General Public License version 3.0 as published by the Free Software
** Foundation and appearing in the file LICENSE.GPL included in the
** packaging of this file.  Please review the following information to
** ensure the GNU General Public License version 3.0 requirements will be
** met: http://www.gnu.org/copyleft/gpl.html.
**
** If you are unsure which license is appropriate for your use, please
** contact the sales department at qt-sales@nokia.com.
** $QT_END_LICENSE$
**
****************************************************************************/

/*!
    \class Q3MemArray
    \brief The Q3MemArray class is a template class that provides arrays of simple types.
    \compat

    Q3MemArray is implemented as a template class. Define a template
    instance Q3MemArray\<X\> to create an array that contains X items.

    Q3MemArray stores the array elements directly in the array. It can
    only deal with simple types (i.e. C++ types, structs, and classes
    that have no constructors, destructors, or virtual functions).
    Q3MemArray uses bitwise operations to copy and compare array
    elements. 

    The Q3PtrVector collection class is also a kind of array. Like most
    old Qt collection classes, it uses pointers to the contained items.

    Q3MemArray uses explicit sharing with a
    reference count. If more than one array shares common data and one
    of the arrays is modified, all the arrays are modified.

    The benefit of sharing is that a program does not need to duplicate
    data when it is not required, which results in lower memory use
    and less copying of data.

    Example:
    \snippet doc/src/snippets/code/doc_src_q3memarray.qdoc 0

    Program output:
    \snippet doc/src/snippets/code/doc_src_q3memarray.qdoc 1

    Note concerning the use of Q3MemArray for manipulating structs or
    classes: Compilers will often pad the size of structs of odd sizes
    up to the nearest word boundary. This will then be the size
    Q3MemArray will use for its bitwise element comparisons. Because
    the remaining bytes will typically be uninitialized, this can
    cause find() etc. to fail to find the element. Example:

    \snippet doc/src/snippets/code/doc_src_q3memarray.qdoc 2

    To work around this, make sure that you use a struct where
    sizeof() returns the same as the sum of the sizes of the members
    either by changing the types of the struct members or by adding
    dummy members.

    Q3MemArray data can be traversed by iterators (see begin() and
    end()). The number of items is returned by count(). The array can
    be resized with resize() and filled using fill().

    You can make a shallow copy of the array with assign() (or
    operator=()) and a deep copy with duplicate().

    Search for values in the array with find() and contains(). For
    sorted arrays (see sort()) you can search using bsearch().

    You can set the data directly using setRawData() and
    resetRawData(), although this requires care.
*/

/*! \fn Q3MemArray::operator QVector<type>() const

    Automatically converts the Q3MemArray<type> into a QVector<type>.
*/

/*! \typedef Q3MemArray::Iterator
    A Q3MemArray iterator.
    \sa begin() end()
*/
/*! \typedef Q3MemArray::ConstIterator
    A const Q3MemArray iterator.
    \sa begin() end()
*/
/*! \typedef Q3MemArray::ValueType
    \internal
*/

/*!
    \fn Q3MemArray::Q3MemArray()

    Constructs a null array.

    \sa isNull()
*/

/*!
    \fn Q3MemArray::Q3MemArray( int size )

    Constructs an array with room for \a size elements. Makes a null
    array if \a size == 0.

    The elements are left uninitialized.

    \sa resize(), isNull()
*/

/*!
    \fn Q3MemArray::Q3MemArray( const Q3MemArray<type> &a )

    Constructs a shallow copy of \a a.

    \sa assign()
*/

/*!
    \fn Q3MemArray::Q3MemArray(const QVector<type> &vector)

    Constructs a copy of \a vector.
*/

/*!
    \fn Q3MemArray::Q3MemArray(int arg1, int arg2)

    Constructs an array \e{without allocating} array space. The
    arguments \a arg1 and \a arg2 should be zero. Use at your own
    risk.
*/

/*!
    \fn Q3MemArray::~Q3MemArray()

    Dereferences the array data and deletes it if this was the last
    reference.
*/

/*!
    \fn Q3MemArray<type> &Q3MemArray::operator=( const Q3MemArray<type> &a )

    Assigns a shallow copy of \a a to this array and returns a
    reference to this array.

    Equivalent to assign( a ).
*/

/*!
    \fn type *Q3MemArray::data() const

    Returns a pointer to the actual array data.

    The array is a null array if data() == 0 (null pointer).

    \sa isNull()
*/

/*!
    \fn uint Q3MemArray::nrefs() const

    Returns the reference count for the shared array data. This
    reference count is always greater than zero.
*/

/*!
    \fn uint Q3MemArray::size() const

    Returns the size of the array (maximum number of elements).

    The array is a null array if size() == 0.

    \sa isNull(), resize()
*/

/*!
    \fn uint Q3MemArray::count() const

    Returns the same as size().

    \sa size()
*/

/*!
    \fn bool Q3MemArray::isEmpty() const

    Returns TRUE if the array is empty; otherwise returns FALSE.

    isEmpty() is equivalent to isNull() for Q3MemArray (unlike
    QString).
*/

/*!
    \fn bool Q3MemArray::isNull() const

    Returns TRUE if the array is null; otherwise returns FALSE.

    A null array has size() == 0 and data() == 0.
*/

/*!
    \fn bool Q3MemArray::resize( uint size, Optimization optim )

    Resizes (expands or shrinks) the array to \a size elements. The
    array becomes a null array if \a size == 0.

    Returns TRUE if successful, or FALSE if the memory cannot be
    allocated.

    New elements are not initialized.

    \a optim is either Q3GArray::MemOptim (the default) or
    Q3GArray::SpeedOptim. When optimizing for speed rather than memory
    consumption, the array uses a smart grow and shrink algorithm that
    might allocate more memory than is actually needed for \a size
    elements. This speeds up subsequent resize operations, for example
    when appending many elements to an array, since the space has
    already been allocated.

    \sa size()
*/

/*!
    \fn bool Q3MemArray::resize( uint size )

    \overload

    Resizes (expands or shrinks) the array to \a size elements. The
    array becomes a null array if \a size == 0.

    Returns TRUE if successful, i.e. if the memory can be allocated;
    otherwise returns FALSE.

    New elements are not initialized.

    \sa size()
*/

/*!
    \fn bool Q3MemArray::truncate( uint pos )

    Truncates the array at position \a pos.

    Returns TRUE if successful, i.e. if the memory can be allocated;
    otherwise returns FALSE.

    Equivalent to resize(\a pos).

    \sa resize()
*/

/*!
    \fn bool Q3MemArray::fill( const type &v, int size )

    Fills the array with the value \a v. If \a size is specified as
    different from -1, then the array will be resized before being
    filled.

    Returns TRUE if successful, i.e. if \a size is -1, or \a size is
    != -1 and the memory can be allocated; otherwise returns FALSE.

    \sa resize()
*/

/*!
    \fn void Q3MemArray::detach()

    Detaches this array from shared array data; i.e. it makes a
    private, deep copy of the data.

    Copying will be performed only if the \link nrefs() reference
    count\endlink is greater than one.

    \sa copy()
*/

/*!
    \fn Q3MemArray<type> Q3MemArray::copy() const

    Returns a deep copy of this array.

    \sa detach(), duplicate()
*/

/*!
    \fn Q3MemArray<type> &Q3MemArray::assign( const Q3MemArray<type> &a )

    Shallow copy. Dereferences the current array and references the
    data contained in \a a instead. Returns a reference to this array.

    \sa operator=()
*/

/*!
    \fn Q3MemArray<type> &Q3MemArray::assign( const type *data, uint size )

    \overload

    Shallow copy. Dereferences the current array and references the
    array data \a data, which contains \a size elements. Returns a
    reference to this array.

    Do not delete \a data later; Q3MemArray will call free() on it
    at the right time.
*/

/*!
    \fn Q3MemArray<type> &Q3MemArray::duplicate( const Q3MemArray<type> &a )

    Deep copy. Dereferences the current array and obtains a copy of
    the data contained in \a a instead. Returns a reference to this
    array.

    \sa copy()
*/

/*!
    \fn Q3MemArray<type> &Q3MemArray::duplicate( const type *data, uint size )

    \overload

    Deep copy. Dereferences the current array and obtains a copy of
    the array data \a data instead. Returns a reference to this array.
    The size of the array is given by \a size.

    \sa copy()
*/

/*!
    \fn Q3MemArray<type> &Q3MemArray::setRawData( const type *data, uint size )

    Sets raw data and returns a reference to the array.

    Dereferences the current array and sets the new array data to \a
    data and the new array size to \a size. Do not attempt to resize
    or re-assign the array data when raw data has been set. Call
    resetRawData(\a data, \a size) to reset the array.

    Setting raw data is useful because it sets Q3MemArray data without
    allocating memory or copying data.

    Example I (intended use):
    \snippet doc/src/snippets/code/doc_src_q3memarray.qdoc 3

    Example II (you don't want to do this):
    \snippet doc/src/snippets/code/doc_src_q3memarray.qdoc 4

    \warning If you do not call resetRawData(), Q3MemArray will attempt
    to deallocate or reallocate the raw data, which might not be too
    good. Be careful.

    \sa resetRawData()
*/

/*!
    \fn void Q3MemArray::resetRawData( const type *data, uint size )

    Removes internal references to the raw data that was set using
    setRawData(). This means that Q3MemArray no longer has access to
    the \a data, so you are free to manipulate \a data as you wish.
    You can now use the Q3MemArray without affecting the original \a
    data, for example by calling setRawData() with a pointer to some
    other data.

    The arguments must be the \a data and length, \a size, that were
    passed to setRawData(). This is for consistency checking.

    \sa setRawData()
*/

/*!
    \fn int Q3MemArray::find( const type &v, uint index ) const

    Finds the first occurrence of \a v, starting at position \a index.

    Returns the position of \a v, or -1 if \a v could not be found.

    \sa contains()
*/

/*!
    \fn int Q3MemArray::contains( const type &v ) const

    Returns the number of times \a v occurs in the array.

    \sa find()
*/

/*!
    \fn void Q3MemArray::sort()

    Sorts the array elements in ascending order, using bitwise
    comparison (memcmp()).

    \sa bsearch()
*/

/*!
    \fn int Q3MemArray::bsearch( const type &v ) const

    In a sorted array (as sorted by sort()), finds the first
    occurrence of \a v by using a binary search. For a sorted
    array this is generally much faster than find(), which does
    a linear search.

    Returns the position of \a v, or -1 if \a v could not be found.

    \sa sort(), find()
*/

/*!
    \fn type &Q3MemArray::operator[]( int index ) const

    Returns a reference to the element at position \a index in the
    array.

    This can be used to both read and set an element. Equivalent to
    at().

    \sa at()
*/

/*!
    \fn type &Q3MemArray::at( uint index ) const

    Returns a reference to the element at position \a index in the array.

    This can be used to both read and set an element.

    \sa operator[]()
*/

/*!
    \fn Q3MemArray::operator const type *() const

    Cast operator. Returns a pointer to the array.

    \sa data()
*/

/*!
    \fn bool Q3MemArray::operator==( const Q3MemArray<type> &a ) const

    Returns TRUE if this array is equal to \a a; otherwise returns
    FALSE.

    The two arrays are compared bitwise.

    \sa operator!=()
*/

/*!
    \fn bool Q3MemArray::operator!=( const Q3MemArray<type> &a ) const

    Returns TRUE if this array is different from \a a; otherwise
    returns FALSE.

    The two arrays are compared bitwise.

    \sa operator==()
*/

/*!
    \fn Iterator Q3MemArray::begin()

    Returns an iterator pointing at the beginning of this array. This
    iterator can be used in the same way as the iterators of
    Q3ValueList and QMap, for example.
*/

/*!
    \fn Iterator Q3MemArray::end()

    Returns an iterator pointing behind the last element of this
    array. This iterator can be used in the same way as the iterators
    of Q3ValueList and QMap, for example.
*/

/*!
    \fn ConstIterator Q3MemArray::begin() const

    \overload

    Returns a const iterator pointing at the beginning of this array.
    This iterator can be used in the same way as the iterators of
    Q3ValueList and QMap, for example.
*/

/*!
    \fn ConstIterator Q3MemArray::end() const

    \overload

    Returns a const iterator pointing behind the last element of this
    array. This iterator can be used in the same way as the iterators
    of Q3ValueList and QMap, for example. 
*/